1. Field of the Invention
This invention relates to a magnetic substance detecting device employing a magnetic sensor.
2. Description of the Prior Art
In the prior art, when a magnetic substance is brought to the vicinity of a reed switch, the reed switch is closed in response to a line of magnetic force of high density in the neighborhood to the surface of the magnetic substance, thus detecting the magnetic substance. However, since opening and closing of the reed switch take place at its contacts, it is likely to cause break down of the switch and, further, the opening and closing operation is achieved by the magnetic attracting force and spring action of iron pieces, so that an increase in sensitivity causes the operation to become unstable in terms of its characteristics and with respect to surrounding conditions. Therefore, it is necessary to lower the sensitivity for stabilizing the operation.